In tanks, boats and the like, sealing washers are employed with headed fasteners such as screws, bolts, nails or the like to seal the fastener hole against leakage of fluid. One known sealing washer is an annular rubber washer which may be positioned in customary manner between the head of a fastener and the part being fastened. Upon tightening of the fastener, the opposed axial surfaces of the rubber washer will effect a seal between the underside of the fastener head and the surface of the part being fastened. Such rubber sealing washer is provided in a variety of forms such as an O-ring and the same may be employed effectively in many situations. However, one drawback of such rubber sealing washer is that under substantial tightening forces, the rubber washer tends to extrude radially between the fastener head and the fastened part which may lead to reduced effectiveness of the seal and/or may contribute to early failure of the rubber washer. Also, the rubber washer is not usually considered decorative in appearance and thus is undesirable for use in articles where the appearance thereof is important. For example, in the manufacture of boats, it is desirable to seal the fastener openings thereof while also providing a decorative accent to the boat.
Another known sealing washer is commonly referred to as a gasket seal and such gasket seal includes a disc-like flat metal body to which is molded on one side thereof an O-ring seal. Again, such as gasket seal has many desirable uses, but is subject to the same undersirable radial expansion of the O-ring seal when subjected to substantial tightening forces of the fastener as is the above noted rubber sealing washer. Moreover, such gasket seal depends at least partly upon metal-to-metal contact for effecting a seal between the fastener head and sealing washer. Also, such gasket seal is not known for its decorative appearance.
Other important considerations in the art of sealing washers, in addition to the ability to withstand substantial tightening forces and to be decorative in appearance, is that the sealing washers be inexpensive and easy to manufacture. It is also desirable that the sealing washers provide a stress relief capability, a fastener locking capability and a vibration damping capability.
While sealing washers are principally employed to seal fastener openings, check valves are employed in numerous arrangements essentially to permit and/or control passage of fluid through the check valve in one direction when the pressure differential across the valve exceeds a predetermined amount. Known check valves come in a variety of forms and constructions and may be used in many ways. It would be advantageous, however, to provide yet another check valve which is inexpensive and easy to manufacture, which can withstand substantial pressures and flows, and which may be readily inserted into existing fitting openings in parts for use in controlling flow through such fitting.